Preparation of aliphatic peracids by oxidation of aldehydes



J. E. aLUDwoRTH 2,314,385

PREPARATION OF ALIPHATIC PERACIDS BY OXIDATION `OF ALDEHYDES Marh 23, 1943.

Filed Feb. .21, 1940 mt 5 rumt.

NvEN-ron Joseph E. BudworH'1`` y f Patented Mar. 23, 1943 PREPARATION or ALrPnA'rrc rEnAoms BY oinnArioN or ALnEmmEs Joseph E. Bludworth,` Cumberland, Md., assigner to Cclanese Corporation of America, a corporation of Delaware Application February 21 1940, Serial No. 320,083 6 Claims. (Cl. 260-502) This invention relates to the oxidation of aliphatic aldehydes to the corresponding per acids and relates more particularly to theirv oxida-4 tion by means of air or other oxygen containing gas.

An object of this invention is the oxidation of aliphatic aldehydes to the corresponding per acids in the vapor phase. Another vobject of this invention is the production of the per acids in high yields and their separation from the reaction products.

It has now been found that aliphatic aldehydes and particularly acetaldehyde may be directly oxidized to the corresponding aliphatic per acids.

The oxidation goes very smoothly when carried out in the vapor phase and in the presence of oxygen.

According to this novel process the aliphatic aldehyde and air are mixed in predeterminedV quantities and then introduced into a preheater which serves to preheat the reactants before their entrance into a reaction chamber. The temperature of the reactants is raised in the reaction chamberand during passage through the chamber at a predetermined linear velocity the oxidation of the aldehyde to per acid takes place. The reaction mixture is then passed to a fractionating column together with a predetermined quantity of benzene and is separated from the per acid by azeotropic distillation. Theuncondensed gases,'the unreacted aldehyde and the by-products are taken oi at the top of the column as an azeotrope with benzene and the per acid is removed at the base. The unreacted aldehyde is absorbed in water. distilled and recycled to the found that certain conditons must be adhered to and these various conditions are set out hereinafter.

The reaction in which aliphatic aldehydes may be `oxidized to aliphatic per acids can be made to proceed smoothly and controllably when the oxidation is carried out in the presence of air. While air is preferably used as the oxidant, free oxygen may also be used, so long as the only reacting component of the gaseous mixture is the oxygen contained therein. All other components should be inert. The amountof air which enters the system must be carefully controlled so that the amount of oxygen present is only sufficient to oxidize the yaldehyde to the per acid and not carry the oxidation to a point where undesirable side vreactions take place. To accomplish this result the air is carefully metered and only approximately 30% oi the theoretical amount of oxygen necessary to oxidize the aldehyde in the reaction zone is forced into the preheaterand thence into the reaction zone by the blowers.

The reacting gases may iirst be brought up to a temperature of approximately 200 F. or more in the preheater. When the gases are thus partly .heated in the preheater, the reaction may be better controlled when the temperature of the gases is finally brought up to reaction temperature in the reaction chamber. Preheating avoids the dangers of any local overheating and any excessive oxidation which might occur if the temperature of the gases were'brought up to the reaction temperature directly in the reaction chamber and without any preheating. The heat ing may be carried out by means of steam or by any other suitable means.

The linear velocity 'of the reacting gases through the preheater and the reaction chamber proper may be varied' from about 30 to about 300 ft./sec. with the velocity preferably about 60 ft./sec. The greater the cross-sectional area of the tubing through which the gases pass the greater must be the volume velocity in order to maintain the desired linear velocity. Increased linear velocity insures the rapid removal ofthe desired product from the reaction zone before any secondary reactions set in, produces a high degree of turbulence which eliminates localized heating, increases heat transfer by decreasing lmthickness and constantly redistributes the reactants to such a degree that the reaction iollows a course which can be predetermined and controlled.

Thetime during which the reactants remain in the reaction zone and are subjected to the heat ofrreaction is short and may vary from about 0.1 second to about 1 second," preferably aboutl 0.2 second.

The temperature at which the reaction takes place may vary from about 350 F. tov about 450 F. and preferably from about 375 F. to about 400 F. In order to attain these reaction temperaoxygen or any gaseous mixture containing free tures, the reactants may be preheated to tem- 4peratures oi about 200 F. or more. The pressure in the preheater and reactor may be as high as 50 pounds per square inch. While such higher pressures are operative it is'preferable to operate at substantially atmospheric pressure to minimize any polymerization of the aldehyde.

lThe use of oxidation catalysts has usually not been found to materially increase the yields of per acids. While the use of such catalysts is not excluded it is preferably to operate with the reaction zone devoid of catalyst material.

In order further to illustrate the invention, but 'without being limited thereto, the following specific example is given, reference being had to the accompanying drawing, all the parts being by weight.

Example parts per minute of acetaldehyde from raw feed supply pipe I are mixed-'with 24.6 parts byinto the inlet of preheater 5.' About 22 parts per minute of air are introduced b'y blower 6 through meter 1, mixed with 170 parts per minute of hot recycle gases from blower 8 and meter 9 taken from the outlet of reaction chambenl, and introduced into preheater 5 along with the 34.6

' parts per minute acetaldehyde above referred to.

In preheater 5 the mixture of gases is raised to 200 F. whence they flow to reaction chamber I0 where they reach a final temperature of approximately 385 F. After leaving the reaction chamber, 142 parts per minute of benzene are introduced into the reaction gases by way of recycle line II. This mixture of reaction products and benzene are passed into fractionation column I2 which operates under a vacuum with the pressure being about 3 pounds per square inch absolute. The uncondensable, gases together with the unreacted acetaldehyde and the constant boiling mixture `formed by the benzene and acetic acid, pass over from the top of the column. 6.65

parts per minute of peracetic acid are withdrawn from the reboiler I3.

In accumulator I4 the uncondensable gases (nitrogen, etc.) and the uncondensed portion of acetaldehyde are separated from the condensed products and withdrawn by means of vacuum pump 15 and fed to water absorber I6 where the vapors are scrubbed by approximately 250 parts per minute of water, the latter absorbing the acetaldehyde. The water and acetaldehyde are removed from absorber IB by pump I1 and fed to distilling column I8 whence the acetaldehyde, after beingstripped from the water, is recycled to feed pumpg; through line 2. The acetaldehyde-free water is removed from reboiler I9 and discharged to waste. The condensed products in accumulator I4, consisting of benzene. acetic acid and some acetaldehyde are withdrawn by pump 20 and fed to fractionation column 2| where the acetaldehyde is separated and then' re'' cycled to pump 3. The benzene and acetic acid are discharged from reboiler 22, through line 23,-

4withdrawn from bottom of decanter and may be sent to any conventional acetic. acid recovery un'it. The acid free benzene is removed from top of decanter and recycled through line II to the feed inlet ci fractionation column I2.

While the above reaction has been described more particularly with reference to the preparation of peracetic acid from acetaldehyde, other aldehydes such as propionaldehyde, butyraldehyde,va1eric aldehyde, caproic aldehyde and other higher aldehydes may .be converted into their respective per acids by this process.

It is to be understood'that the foregoing detailed description and drawing is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of aliphatic peracids from the corresponding aliphatic aldehyde, which comprises oxidizing said aldehyde by preheating the vapor of said aldehyde to about 200 F. in admixture with an amount of oxygen theoretically insufiicient to oxidize more than about 30% 'of said aldehyde to the per-acid, and passing the preheated mixture at a linear velocity of at least 30 feet per second through a reaction zone at a temperature of 350 to 450 F., the time of contact being from 0.1 to about 1 second and the pressure being substantially equal to atmospheric pressure.

2. Process for the production of per-acetic acid from the corresponding aldehyde which comprises oxidizing said aldehyde by preheating the vapor of the aldehyde to about 200 F. in admixture with an amount of oxygen theoretically insumcient to oxidize more than about 30% of .the aldehyde to per-acid, and passing the preheated mixture at about 60 ft. per second through a reaction zone at a temperature of 350 to 450 F., the time of contact being about 0.2 second and the pressure being substantially equal to atmospheric pressure.

3. Process for the production of per-acetic acid from the corresponding aldehyde which comprises oxidizing said aldehyde by preheating the vapor of the aldehyde to about 200 F. in ad- 4mixture with an amount of oxygen theoretically insufcient to oxidize more than about 30% of the aldehyde to per-acid, and passing the preheated mixture at about 60 ft. per second through a reaction zone at a temperature of 350 to 450 F., the time or contact being about 0.2 second and the pressure being substantially equal to atmospheric pressure, the greater part ot the gaseous mixture emerging from the reaction zone being recycled to said zone and the remainder being treated for recovery o! the per-acid.

4. Process for the production of per-acetic acid from the corresponding aldehyde. whichA comprises oxidizing said aldehyde by preheating the vapor of the aldehyde to about 200 F. in admixture with an amount of oxygen theoretically insufficient to oxidize more than about 30% of the aldehyde to per-acid, and passing the preheated mixture at about 60 ft. per second through a reaction zone at a temperature of 350 to 450 F., the time of contact being about 0.2 second and the pressure being substantially equal to atmospheric pressure, mixing benzene vapor with the gaseous mixture removed from the re- -'action zone for recovery of the per-acetic acid,

- hyde and uncondensable gases, from the peracid, by fractionation.

l5. Process for the production of aliphatic peracids from the corresponding aliphatic aldehyde.

which comprises oxidizing said aidehyde by preheating the vapor of said aldehyde to about 200 F. in admixture with an amount of oxygen theoretically insufcient to oxidize more than about 30% of said aldehyde to the per-acid, and passing the preheated mixture at a. linear velocity or at least 30 feet per second through a reaction zone at a temperature of 350 to 450 F., the time of contact being from 0.1 to about 1 second and the pressure being substantially equal to atmospheric pressure, the greater part of the gaseous mixture emerging from the reaction zone being recycled to said zone and the remainder being treated for recovery of the per-acid.

6. Process for the production of aliphatic neracids !rom the corresponding aliphatic aldehyde, which comprises oxidizing said aldehyde by preheating the vapor of said aldehyde to about 200 F. in admixture with an amount of oxygen theoretically insuilcient to oxidize more than about 30% of said aldehyde to the per-acid, passing the preheated mixture at a linear velocity of at least qjeet per second through a reaction zone at a. tenperature of 35o to 540 F., the time of contact being from 0.1 to about l second and the pressure being substantially equal to atmospheric pressure, mixing benzene vapor with the l gaseous mixture removed from the reaction zone for the recovery of the per-acid, forming an azeotropic mixture with the aliphatic acidr` formed as a by-product, and removing said azeotropic mixture, together with unreacted aldehyde and uncondensable gases from the per-acid, by

fractionation.

JOSEPH E. BLUDWORTH.

CERTIFICATE oF CORRECTION. Patent No. 2,511+,585. l March 25, 19145.

JOSEPH E. BLuDwom'H.l

It is hereby certified that er'ror appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 6, for "5h00 iF." read --lpj-Oo F.; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the cese in the Patent Office.

Signed and sealed this Lith day of May, A( D. 19h57 Henry Van Az'sdale, (Seal) Acting Commissioner of Ptents. 

